title: Relationship between touch impairment and brain activation after lesions of subcortical and cortical somatosensory regions.
abstract: BACKGROUND
  The neural basis underlying somatosensory impairment and recovery poststroke is virtually unexplored.
  
  
  OBJECTIVE
  To investigate the relationship between touch discrimination impairment and task-related brain activation in stroke survivors with somatosensory impairment following subcortical or cortical lesions.
  
  
  METHODS
  A total of 19 stroke survivors with touch impairment were investigated using fMRI and a touch discrimination paradigm 1-month poststroke; 11 had subcortical and 8 cortical sensory lesions; 12 age-matched healthy controls were also studied. Mean task-related contrast images were regressed with sensory impairment using random effects analysis for each subgroup and the total group.
  
  
  RESULTS
  There was no significant difference in touch impairment between stroke subgroups. Touch discrimination of the affected hand correlated negatively with task-related activation in the ipsilesional primary somatosensory cortex (SI; adjacent to the SI hand area activated in healthy controls); ipsilesional secondary somatosensory cortex (SII); contralesional thalamus; and attention-related frontal and occipital regions in the subcortical group. In contrast, the cortical group did not show significant correlated activity. Yet there was no significant between-group difference in a priori somatosensory regions: only in the superior medial frontal gyrus. A negative correlation was observed in the contralesional thalamus for the total group, irrespective of lesion type.
  
  
  CONCLUSIONS
  The findings provide novel evidence of neural correlates of poststroke touch impairment involving a distributed network of ipsilesional SI and SII, the contralesional thalamus, and frontal attention regions, particularly following subcortical lesions. Further systematic investigation of a modulatory role for ipsilesional SI, the thalamus, and frontal attention regions in sensory processing and recovery is warranted, particularly given implications for rehabilitation.
authors.affiliation: National Stroke Research Institute, Florey Neuroscience Institutes, Melbourne, Victoria, Australia. lcarey@nsri.org.au
authors.forename: Leeanne M
authors.initials: LM
authors.lastname: Carey
authors.forename: David F
authors.initials: DF
authors.lastname: Abbott
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Harvey
authors.forename: Aina
authors.initials: A
authors.lastname: Puce
authors.forename: Rüdiger J
authors.initials: RJ
authors.lastname: Seitz
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Donnan
mesh_terms: D000328:Adult; D000368:Aged; D001288:Attention; D001921:Brain / Q000503:physiopathology*; D004192:Discrimination, Psychological; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012678:Sensation Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology*; D013003:Somatosensory Cortex / Q000503:physiopathology*; D020521:Stroke / Q000150:complications*; D000071939:Stroke Rehabilitation; D013788:Thalamus / Q000503:physiopathology; D014110:Touch